Many developments in the field of bimetallic thermostats have attempted to deal with and avoid creep in the thermostat. A particular method of accomplishing this has been through the use of a formed, dish-shaped portion within the bimetal. Because the dish-shaped portion actually snaps from one position to another at the desired temperature, this forming technique has avoided many of the problems of creeping in bimetallic thermostats. The use of such dish-shaped portions is shown, for example, in U.S. Pat. Nos. 2,820,870 and 3,443,259.
However, many bimetallic thermostats require a rectangular strip for proper functioning. The formed, dish-shaped member can be, and usually is, provided at the center of this rectangular strip. While the problems of creep are minimized with such a construction, they are not entirely avoided. In fact, various adjustments can be made in order to avoid creep, but the creep is only avoided on opening of the contact, or on closing of the contact, and not on both.
Generally, in a construction of the type described, the bimetallic strip, with the dish-shaped portion, is placed within a rectangular casing so as to act against an arm on which a contact is mounted in order to make and break the circuit contact. Because of the construction of the bimetallic strip, the "tails," those portions of the bimetallic strip beyond the dish-shaped portion, will begin to press against the bottom of the casing as the temperature rises. Even prior to snapping of the dish-shaped portion, the edges of that portion will begin to bear against the contact arm and moves it slightly from the fixed contact which it abuts when contact is made. This is the type of creep which it is desired to avoid with the construction of the present invention.